This invention relates to automated machinery for winding flat filaments, in particular optical fiber ribbons, onto a take-up reel.
The prior art includes many devices for winding cables, filaments, or the like. Many automated winding devices include a mechanism for traversing the filament from side to side in a direction parallel to the axis of the take-up reel. In addition, some devices provide for an outward radial adjustment of a traverse guide arm to accommodate the increasing diameter of the windings already on the reel. The goal of many winding devices is to wind the filament onto the take-up reel in smooth layers without leaving bunches or gaps into which the filament may fall as the next outermost layer is wound. This invention principally concerns an improved device for the outward radial adjustment of a winding mechanism in which a guide means, such as a deflection sheave or guide arm, dispenses the filament onto the take-up apparatus.
In prior art winding devices, a guide arm typically is used to guide the rope, cable, wire, or yarn onto the drum of a take-up device, usually a reel. The guide arm is typically an elongated bar with a hole at its distal end. The filament to be wound is threaded through this hole. As the filament is wound, the guide arm moves, and the filament is directed to a desired position by the force exerted thereon by the guide arm. In the alternative, the traverse may be accomplished by keeping the traverse guide arm in a fixed position and traversing the take-up reel along its axis.
Some prior art winding devices act to press the filament into its desired position through the action of an elongate bar which presses on the filament as it contacts the drum or the previously wound filament package. An example of such a winding device is described in U.S. Pat. No. 3,951,355. This bar may be an extension of the guide arm or may be a separate structure.
Flat filaments are more difficult to wind than cylindrical filaments. Flat filaments bend more easily in some directions than in other directions, which may result in asymmetrical forces which cause the flat filament to behave unpredictably, particularly as the number of forces on the filament increase. Cross-sections of flat filaments have a non-uniform exterior profile, as compared to a cylindrical filament, making it more important to keep the flat filament from twisting onto its side while being wound.
Optical fiber ribbons are flat filaments which typically include a parallel array of coated optical fibers which are enclosed within at least one layer of polymer material having an external rectangular cross-section with rounded corners. Optical fibers can be damaged by external forces placed upon them. Excessive bending, rubbing or twisting of the optical fiber ribbons can lead to physical damage to the ribbons which can cause excess attenuation of the light passing through the optical fibers therein. Because of these concerns, optical ribbon winding devices have been operated at low speeds to avoid any damage to the optical fiber ribbons. Low production speeds in turn increase manufacturing costs of optical fiber ribbon cablers.
The ribbon outer common coating typically has a minimum coefficient of friction. For this reason, it is impractical to push a ribbon across the surface of another ribbon to adjust its position. Precise initial placement of the ribbon onto the take-up reel is of paramount importance in preventing physical damage to the ribbon and possible excessive increases in optical fiber attenuation.
It is therefore an object of the present invention to provide an optical fiber ribbon winding apparatus capable of operation at higher speeds than allowed by previous winding apparatus.
Another object of the invention is to provide an optical fiber ribbon winding apparatus which less frequently causes damage to the ribbon being wound, and may or may not utilize a guide arm to mechanically guide the optical fiber ribbon between the final deflection sheave and the take-up reel.
Still another object of the invention is to provide an optical fiber ribbon winding apparatus including an improved movement system to accommodate an accumulating filament package on the take-up reel.
Yet another object of the invention is to keep the optical fiber ribbon within an essentially vertical plane as it is being wound.
These and other objects are provided, according to the present invention, by a winding machine comprising a carriage bearing a guide means. The flat filament is directed by said guide means to be dispensed onto the take-up reel, where the filament is wound continuously in accumulating layers. The take-up reel is traversed back and forth parallel to its own axis in a manner well known to the art. The tension on the flat filament is monitored and controlled. A first proximity sensor mounted to the carriage senses the position of the outermost accumulating filament layer when it is within a predetermined distance. Information from the first proximity sensor is transmitted to a programmable logic controller.
It is necessary to prevent the guide means from impinging against the flanges of the take-up reel. The controller may be programmed to cause the ends of the filament layers to be spaced apart by a greater distance from the reel flanges after a predetermined number of filament layers have been wound. After the predetermined number of filament layers have been wound, the winding may assume a trapezoidal shape in cross-section. The programmable logic controller may cause the carriage to move the guide means forward, toward the take-up reel, when a predetermined length of filament has been dispensed, or, equivalently, when a predetermined number of layers of filament have been wound onto the take-up reel. Thus, the carriage is moved forward only when there exists sufficient spacing between the ends of the outermost filament layer and the respective flanges to provide clearance for the guide means.
After the carriage has been moved forward, the proximity sensor detects the presence of the accumulating outermost filament layer on the take-up reel, and the programmable logic controller activates the carriage as needed to maintain the guide means within a predetermined range of distance from the outermost filament layer. Thus, the carriage and guide means are moved sequentially to positions at a greater radial distance from the take-up reel longitudinal axis as the filament layers accumulate onto the take-up reel.
The invention allows the length of free ribbon between the guide means and the outermost layer of ribbon on the take-up reel to be minimized, thereby minimizing the amplitude of any vibration or other path perturbation which could compromise the quality of the winding.